Fret by fret
Guitar intonation tester
Intonation here means one comparison: the note you just played against the equal-tempered pitch for that fret. The 12th fret should be twice the open-string frequency, one octave up. Frets in between follow the twelfth root of two. You choose the string and the fret, then save a reading if you want a short log.
What the number cannot decide
Nut slots, saddle position, relief, action, temperature, how hard you press and where the microphone sits all move the cents. A reading that is sharp at the 12th fret is a note for you or a technician. This page will not tell you to file a saddle, and it cannot see whether the fret itself is worn. Carry the log if it helps the conversation. Do not treat it as a verdict.
How to take a useful reading
Tune the open string on the main tuner first. Then fret lightly, just behind the fret wire, and pluck once. Wait until the pitch settles before you log it. Checking every fret on one string tells you more than one heroic reading at the 12th. The chromatic tuner is the free-form cousin of this page; this one keeps the target tied to a fret.
Questions
- Should the 12th fret match the harmonic?
- On a settled guitar they are close, both an octave above the open string. If they disagree, write both numbers down. The page still does not say which part to move.
- Does it listen to all six strings at once?
- No. Pick one string in the menu and mute the others. Two notes at once make the cents meaningless.